Method for hydrating paper stock



Sept. 2, 1947. E. cowuzs 2,426,923

METHOD FOR HYDRATING PAPER STOCK Filed Dec. s1, 1942 2 Sheets-Sheet 1 Sept. 1947- E. cowuzs 2,426,923-

METHOD FOR 'HYDRATING PAPER STOCK Filed Dec. 31, 1942 2 Sheets-Sheet 2 Willi!" v a i h Q INVENTOR u I LVMIMMISK ATTORNEYS Patented Sept. 2, 1947 METHOD FOR HYDRATING PAPER STOCK Edwin Cowles, Cayuga, N. Y., assignor to The Cowles Company, Princeton, N. .l'., a corporation of New Jersey Application December 31, 1942, Serial No. 470,730

2 Claims. 1,

This invention relates to methods for hydrating paper stock.

In processes for the preparation of paper stock for use in the manufacture of paper it is usually desirable 1) to completely defiber the stock, 1. e. separate the individual fibers of the stock one from another, (2) to cut the fibers to the desired length, and (3) to hydrate the stock, 1. e. cause the fibers to absorb a certain amount of water. The degree of hydration of stock is indicated in part by its freeness, and by the amount that a newly formed sheet of paper shrinksupon drying. In general a well hydrated stock produces a stronger sheet than would be produced from a similar stock less well hydrated.

These three objectives are usually accomplished in beaters or in a combination of heaters and Jordans or similar equipment set or adjusted within the skill of the operator to produce the desired result, particularly the desired balance between cutting and hydrating. The principal factors in such adjustment are the sharpness of the bars of the roll and bedplate, the clearance between theroll and bedplate, rate of rotation of the roll, and time of treatment. The difliculty in effecting the desired adjustment arises from the fact that in the operation of heaters and Jordans cutting and hydration proceed simultaneously, and while it is possible, by adjustment, to cause either cutting or hydration to predominate, the other efiect'almost inevitably results also, and it is only by long experience and careful observation that the operator is enabled to secure the desired results.

It is an object of the present invention to pro- Vide a method for hydrating paper stock without Other objects and advantages of the invention will appear hereinafter.

A preferred embodiment of the invention selected for purposes of illustration is shown in the accompanying drawings, in which,

Figure l is a top plan view.

Figure 2 is a section on the line 2-2 of Figure 1.

Figure 3 is a top plan view of a modified form.

Figure 4 is a section on the line 44 of Figure 3.

In the practice of my invention, I rotate a member having an abrasive surface at relatively high velocity in a body of stock of relatively high consistency. The said abrasive surface is freely exposed to the body of stock so that the hydrating action 'results solely from the action of the abrasive surface on the fibersin contact therewith, as distinguished from the action which results member should be rotated at a rate such that the peripheral velocities of the abrasive surfaces of the member should exceed 1000 feet per minute,

and should preferably lie within the range between 2000 and 5000 feet per minute for good capacity and power economy. In cases where,

due to the shape of the rotating member, as hereinafter explained, the velocities at one portion of the rotating surfac differ from the velocities at another portion thereof, it is sufiicient that the major portion of the surface velocities lie within this range.

By relatively high consistency I mean a consistency in excess of 5%. In general the efliciency of the hydrating action increases with the consistency of the stock, and while hydration will occur when working with consistencies less than 5%, the power consumption required to produce a given degree of hydration will be high.

At consistencies above 12% paper stock loses its ability to flow freely and while hydration will proceed to advantage with respect to stock exposed to the abrasive surface, the result may not be uniform. At a consistency of approximately 10% the efficiency is high and the stock is sufli- I ciently free flowing for satisfactory results in apv paratus such as shown in the drawings.

The-abrasive surface employed may be of various types; as for example, a surface of ceramic bonded abrasive grain such as silicon carbide. A metal surface cut or grooved to provide a surface similar to a file surface may be used, and other abrasive surfaces will occur to those skilled in the art.

For best results, the shape of the rotating member should be such as to move smoothly through the body of stock, for the hydrating action results from the abrasive action of the rotating member on the stock which is in contact therewith. I have found that the friction which occurs between the abrasive surface and the stock as hydration proceeds is usually suflicient to induce circulation of stock at the consistencies set forth above, so that in a properly designed, apparatus, as shown in the accompanying drawings, it is unnecessary to additionally propel the stock. Accordingly, the surface of the rotating member should preferably be a surface of revolution, 1. e. a surface formed by moving a line, straight, curved or irregular, about the axis of rotation. Thus the surface should be cylindrical, disk shaped, conical or spherical, for example, rather than a pitched surface such as a screw, worm or propeller. A pitched surface or propelling vanes should be resorted to only in special cases, such as in the case of extremely high consistencies,

where required to induce additional circulation or in the case of batch operation where large quantitles of stock must be circulated.

Referring to the drawings, a simple form of apparatus embodying my invention is shown in Figures 1 and 2, in which the rotating member I has an abrasive surface 2 of cylindrical form. The said member is mounted for rotation in a casing 3, being hung on a shaft 4 carried in a bearing 5, resiliently supported between rubber rings 6 engaging a supporting platform 1. The shaft may be driven by pulley 8. The casing should also be of cylindrical form, preferably of a diameternot greatly exceeding the diameter of the cylinder I, in order that the skin friction of the abrasive surface on the stock may cause circulation of the stock throughout the space between the cylinder and the wall of the casing so as to cause all portions of the stock to be subjected to treatment.

The hydrating operation may be conducted either as a batch operation or as a continuous operation, but in the preferred embodiment illustrated, the apparatus is adapted for continuous operation, the stock being introduced into the casing through a pipe ll entering the bottom of the casing, and leaving the casing through a box [2 mounted on one side of the casing. Located between the casing and the box I2 is an adjustable dam l3 by means of which the level of the stock in the casing may be controlled. This arrangement affords a convenient means of controlling the degree of hydration, for, assuming a constant rate of inflowing stock, the greater the depth of stock in the casing, the longer the time required for the stock to move from the bottom of the casing to a point where it can overflow the dam l3 and the greater the degree of hydration. The degree of hydration may also be controlled, of course, by controlling the rate of inflow of stock to the casing.

If desired, make up water may be introduced into the top of the box 12 at a rate sufficient to reduce the consistency of the stock withdrawn from the casing to any suitable consistency for further operations.

The cylindrical member is rotated to provide peripheral velocities as above set forth, and the skin friction of the abrasive surface, moving through relatively high consistency stock at such velocities, has a tendency to whirl the stock in the casing. In some cases it may be desirable, therefore. to retard this whirling motion, as by the provision of vertical baffles 14 projecting inwardly from the wall of the casing.

A modified form of apparatus is illustrated in Figures 3 and 4 in which the rotating member comprises a series of abrasive disks 2| spaced by cylindrical collars 22, said cylindrical collars also having abrasive surfaces. With this form of rotating member the surfaces of the spaced disks induce a circulation of the stock in the direction indicated by the arrows, and this has been found particularly effective in securing uniform treatment of the stock. In this form of apparatus, in addition to the vertical bafiies, horizontal baffles 23 may be employed to assist in obtaining the desired circulation.

.The process and apparatus of my invention is ordinarily used for the hydration of stock which has been previously defibered. It will be understood, however, that the action of the abrasive surface will have a defibering effect on undeflbered or partially defibered stock so that it is possible to introduce either undefibered or partially defibered stock intothe apparatus, in which case a defibering action may precede or accom pany the hydrating action. One of the remarkable and unexpected results of the process, however, is that hydration of the stock proceeds without perceptible cutting or shortening of the fibers. This is of considerable operating advantage in many instances.

It will be understood that the invention may be variously modified and embodied within the scope of the subjoined claims.

I claim as my invention:

1. Process for hydrating paper stock without perceptible cutting or shortenin of the fibers which comprises rotating a member having an abrasive surface of revolution at relatively high velocity in a body of stock of relatively high consistency, said abrasive surface being freely exposed to the body of stock and rotating smoothly and freely in said body of stock except for the frictional resistance imposed by the stock on said smoothly rotating abrasive surface, and thereby hydrating the pulp solely by the action of the abrasive surface in contact therewith.

2. Process for hydrating paper stock without perceptible cutting or shortening. of the fibers which comprises rotating a member having an abrasive surface of revolution at a peripheral velocity exceeding 1000 ft. per minute in a body of stock having a consistency exceeding 5%, said abrasive surface being freely exposed to the body of stock and rotating smoothly and freely in said body of stock except for the frictional resistance imposed by the stock on said smoothly rotating abrasive surface, and thereby hydrating the pulp solely by the action of the abrasive surface in contact therewith.

EDWIN COWLES.

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